L-ascorbic acid is an indispensable vital ingredient for animals (including aquatic animals) and plays an important role particularly in the synthesis of collagen or the elimination of active oxygen in vivo. Furthermore, L-ascorbic acid is one of very important nutrients for animals as a vitamin having an anti-stress effect. However, L-ascorbic acid is unstable and readily oxidized or degraded to lose its activity. In order to prevent this, use of an L-ascorbic acid-2-phosphoric ester salt as an additive for animal feed has been proposed (see, for example, JP-A-8-124109 (the term "JP-A" as used herein means an "unexamined published Japanese patent application")).
L-ascorbic acid phosphoric ester salt is an excellent vitamin C supply source for animals and usually it is administered to animals in a composition, more specifically, by a known method of blending it in feed, feed raw material, feed additive, feed additive raw material, animal drug or animal drug raw material. On the other hand, in the feeding of useful animals such as cattle, fowl, pets, experimental animals or aquatic animals, problems occur in these useful animals such as aging, depression of resistance against diseases, generation of stress, reduction in hatch ratio, deterioration of egg or meat quality, propagation disorder, mastitis or reduction of somatic cells in milk. Therefore, it has been heretofore keenly demanded to solve these problems.
Particularly, in the feeding of useful animals having a high added value, such as fowl, quail, cattle, pigs, horses, dogs, cats, rats, mice, guinea pigs, monkeys, Japanese river trout, carp, sea bream, salmon, eel, yellowtail, purple blue back bass, globefish, flatfish, tuna, saurel, horse mackerel, blue back bass, green tiger prawn and giant tiger prawn, the production is being performed in a highly efficient manner. However, due to increase in the feeding density, promotion of aging, depression of resistance against diseases, generation of stress, acceleration of oxidation of meat, deterioration of meat quality such as blackening, or increase in propagation disorder tends to occur more frequently. Propagation disorder is caused by premature birth, reduction of conception ratio, ovulatory retardation, death of embryo, weakened estrous symptom, or reduction in the production of progesterone. Furthermore, when mastitis occurs, the number of somatic cells in milk increases and the commercial value of the milk is lowered markedly. For the purpose of treating or preventing the propagation disorder or mastitis, various vitamins including L-ascorbic acid phosphoric ester salts and derivatives thereof, and minerals have been heretofore added, individually or in combination, to the drinking water or feed and then fed to useful mammals.
Poultry such as fowl and quail under overcrowded feeding suffer from depression of resistance against diseases, generation of stress, deterioration of meat quality and propagation disorder, and in the case of poultry for laying, additionally a reduction in egg quality. In order to overcome these problems, various vitamins including L-ascorbic acids and derivatives thereof, and minerals have been heretofore added, individually or in combination, to the drinking water or feed and then fed to poultry.
In aquatic culturing, the aquatic animals under overcrowded feeding suffer from problems of aging, depression of resistance against diseases, generation of stress, deterioration of meat quality, deterioration of egg quality and additionally, reduction in hatching ratio and degradation of the body color. In order to overcome these problems, various vitamins including ascorbic acid phosphoric ester salts and derivatives thereof, and minerals have been conventionally added individually or in combination to the feed or feed additives and then fed to Japanese river trout, carp, sea bream, salmon, eel, yellowtail, globefish, flatfish, tuna, horse mackerel and green tiger prawn.
However, when conventional L-ascorbic acid phosphoric ester salts are supplied to animals, a slight amount of the salt is degraded in the alimentary canal. Furthermore, in a feed having a large water content and containing a phosphoric acid ester hydrolase such as phosphatase, the amount of the salt is slightly reduced. As a result, a 100% dose cannot be supplied to animals. It is confirmed in the tests by the present inventors that water-soluble L-ascorbic acid phosphoric ester salts are very swiftly hydrolyzed by phosphatase present in specific feed raw materials such as wheat.
Conventional L-ascorbic acid phosphoric ester salts are sometimes degraded to 10% or more in the absence of phosphatase or by heating, pressurization or unknown catalyst or enzyme during the production process. The degradation in 10% or more of the L-ascorbic acid phosphoric ester salt added is one of main factors of the serious decrease in the commercial value of feed or the like produced.
Heating or pressurization is applied particularly by special instruments such as pelletizer, extruder and drier. In the case of a pelletizer or drier, the temperature necessary for achieving the purpose is 60.degree. C. or more, and in the case of an extruder, it is 100.degree. C. or more. At the production of feed for special aquatic animals such as yellowtail, purple blue back bass, sea bream and green tiger prawn, where the heating condition is relatively severe, or in the case of special twin-screw extruder, the temperature is 110.degree. C. or more. Under these special conditions, a sparingly soluble L-ascorbic acid phosphoric ester salt is degraded in a few % or more and the addition efficiency disadvantageously decreases.
L-Ascorbic acid phosphoric ester salts are expensive as compared with general vitamin C, therefore, at the addition to relatively inexpensive feed, the depletion efficiency must be restrained to the minimum limit.